1. Field of the Invention
The present invention relates to a vibration motor including a vibration element in which a plurality of different vibrations are combined to generate elliptical vibratory motion. More specifically, the present invention is related to a vibration motor, including a base, a relative moving member, and a vibration absorbing member interposed between the base member and the relative moving member to prevent both the generation of noise and the reduction of driving efficiency by absorbing the vibration of the relative moving member, thereby eliminating the vibration of the base.
2. Description of the Related Art
Vibration motors which use so-called degenerate modes having different form, causing the simultaneous generation of two different vibrations, are disclosed, for example, in the Fifth Dynamic Symposium Relating to Electromagnetic Force, Collected Papers, Tomikawa, page 393.
FIG. 11 is a perspective view of a vibration motor 1 having a vibration element 2 disclosed by the Tomikawa reference. Moreover, FIGS. 12A-12B are illustrative diagrams of the vibration element 2, wherein FIG. 12A is a top view, FIG. 12B is a side view, and FIG. 12C is a diagram showing examples of waveforms representing two different vibrations L1, B4 generated by the vibration element 2.
As shown in FIGS. 11, 12A and 12B, the vibration element 2 includes an elastic member 3 and an electromechanical conversion element 4 (referred to hereinbelow, where appropriate, as a xe2x80x9cpiezoelectric memberxe2x80x9d) which converts electrical energy into mechanical energy.
The respective dimensions of the vibration element 2 are set such that the natural frequencies of the first order longitudinal vibration L1 and the fourth order torsional vibration B4 about coincide. A piezoelectric member 4 having a plurality of electrodes 5a, 5b, 5g, 5p is affixed to one flat surface of the elastic member 3. Moreover, two projecting driving force output members 3a, 3b are formed on a flat side of the elastic member 3, opposite to the side to which the plurality of electrodes 5a, 5b, 5g, 5p are affixed.
As shown in FIGS. 12B and 12C, the driving force output members 3a, 3b are arranged with respect to the length direction of the vibration element 2 in positions which coincide with the outside antinode positions 11, 14 among the four (4) antinode positions 11, 12, 13 and 14 of the bending vibration B4 which is generated by the vibration element 2.
The electrodes 5a, 5b are respectively excited by high frequency drive voltages VA, VB having phase mutually displaced by about xcfx80/2. As shown in FIG. 12C, upon exciting the electrodes 5a, 5b, there simultaneously arise in the elastic member 3 a first order longitudinal vibration L1 and a fourth order bending vibration B4 which vibrates in the thickness direction of the vibration element 2. The combined the longitudinal vibration L1 and the bending vibration B4 generated in the elastic member 3 cause the respective bottom surfaces of the driving force output members 3a, 3b to vibrate in a manner which displaces them circumferentially (referred to herein as elliptical motion). The vibration element 2 is brought into pressure contact with a relative moving member 6 such that the elliptical motion of the driving force output members 3a, 3b moves the relative moving member in relative motion.
In the abovedescribed manner, the vibration element 2 generates a rectilinear relative movement, in the direction of the double arrow in FIG. 11, between the relative moving member 6 and the driving force output members 3a, 3b with which the relative moving member 6 is in pressure contact. Furthermore, in the vibration element 2 using degenerate modes having different form, the longitudinal vibration L1 generated in the vibration element 2 is used as a propulsion force in the driving direction. Moreover, the bending vibration B4 confers a function which propagates the longitudinal vibration L1 intermittently to the relative moving member 6 (referred to herein as a xe2x80x9cclutch functionxe2x80x9d). The clutch function causes rectilinear relative movement to be generated in one direction between the vibration element 2 and the relative moving member 6.
The present applicant has found that when the vibration motor 1 is driven, a base member 7 of the relative moving member 6 vibrates at its natural frequency, and generates noise. The generation of noise is a very serious problem, since silent operation is an important feature of vibration motors.
Moreover, because the relative moving member 6 also vibrates accompanying vibration arising in the base 7, the state of contact between the relative moving member 6 and the driving force output members 3a, 3b of the vibration element 2 becomes poor. Because of the poor contact between the relative moving member 6 and driving force output members 3a, 3b, the clutch function is impeded, driving efficiency decreases, and driving performance becomes poor.
It is an object of the present invention to provide a vibration motor having a vibration element using degenerate modes having different form which overcomes the problems of the conventional vibration motor and eliminates both the generation of noise originating in vibration of the base member, and the decrease of driving efficiency when driving the vibration motor.
The present inventor obtained the following information with respect to the origin of the vibration of the base member 7. Specifically, in the vibration element 2 using degenerate modes having different form, because of the clutch function, the relative moving member 6 is normally in a state in which it is struck by the driving force output members 3a, 3b of the vibration element 2. When the relative moving member 6 is struck by the driving force output members 3a, 3b, vibration is generated in the relative moving member 6 accompanying the striking. The vibration accompanying the striking is transmitted from the relative moving member 6 to the base member 7, causing the base member 7, which generally has a low natural frequency, to vibrate at its own natural frequency.
The present invention is based on the new information that both the generation of noise and the reduction of driving efficiency can be prevented by interposing a vibration absorbing member, which can absorb the vibration of the relative moving member, between the base member and the relative moving member, to thereby eliminate the vibration of the base.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprising a vibration element including a driving force output member, which is excited to produce a combination of plural different vibrations, and generates an elliptical vibration in the driving force output member; a relative moving member in pressure contact with the driving force output member, to move in relative motion with respect to the vibration element; a first base member; a pressure support member, fixed between the vibration element and the first base member, to place the vibration element in pressure contact with the relative moving member; a second base member to support the relative moving member; and a vibration absorbing member to absorb vibration produced by the elliptical vibration generated by the vibration element in at least one of the relative moving member and the pressure support member, the vibration absorbing member being disposed in at least one of between the first base member and the pressure support member, between the pressure support member and the vibration element, and between the relative moving member and the second base member.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprising a vibration element including a driving force output member, which is excited to produce a combination of plural different vibrations, and generates an elliptical vibration in the driving force output member; a relative moving member, in pressure contact with the driving force output member, to move in relative motion with respect to the vibration element; a pressure support member to place the vibration element in pressure contact with the relative moving member; a base member to support the relative moving member and the pressure support member; and a vibration absorbing member to absorb vibration arising in at least one of the relative moving member and the pressure support member produced by the elliptical vibration generated by the vibration element; the vibration absorbing member being disposed in at least one of between the base member and at least one of the relative moving member and the support member, and between the vibration element and the pressure support member.
In accordance with embodiments of the present invention, at least one of the plurality of different vibrations of the vibration motor is in a direction approximately parallel to the direction in which the pressure support member generates pressure force.
In accordance with embodiments of the present invention, the vibration element comprises a plurality of driving force output members, and the phase of the elliptical vibration which is respectively generated in the plurality of driving force output members mutually differs.
In accordance with embodiments of the present invention, the hardness of the driving force output member is at least 75 on the Rockwell M scale.
Furthermore, in accordance with embodiments of the present invention, the vibration absorbing member is united to at least one of the first base member, the second base member, the base member, and the relative moving member.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprising a vibration element including a driving force output member having Rockwell M scale hardness of at least 75, and which generates an elliptical vibration comprising a plurality of different vibrations in the driving force output member; a relative moving member in pressure contact with the driving force output member to move in relative motion with respect to the vibration element; a base member to support at least one of the vibration element and the relative moving member; and a vibration absorbing member to absorb vibration generated by the vibration element, the vibration absorbing member being disposed in at least one of between the base member and the vibration element, and between the relative moving member and the base member.
In accordance with embodiments of the present invention, the vibration motor further comprises an optical switch including at least one first optical fiber which is fixed to the base member, and at least one second optical fiber which is fixed to a portion which is relatively movable with respect to the base member, wherein relative movement of the at least one first optical fiber and the at least one second optical fiber causes optical connection and disconnection of the at least one first optical fiber and the at least one second optical fiber.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprising a vibration element including a driving force output member having a Rockwell M scale hardness of at least 75, and which generates an elliptical vibration comprising of a plurality different vibrations in the driving force output member; a relative moving member in pressure contact with the driving force output member to move in relative motion with respect to the vibration element; a base member to support and fix the vibration element; a pressure support member to provide a force causing the vibration element and the relative moving member to contact under pressure, the pressure support member being disposed between the base member and the vibration element; and a vibration absorbing member between the pressure support member and the vibration element to absorb vibration generated by the vibration element.
In accordance with the present invention, the vibration motor further comprises an optical switch including at least one first optical fiber fixed to a portion which moves relatively with respect to the vibration element, and at least one second optical fiber fixed to a portion which moves relatively with respect to the vibration element, wherein relative movement of the at least one first optical fiber and the at least one second optical fiber causes the optical connection and disconnection of the first optical fibers and the second optical fibers.